Refrigeration



April 29? 1941. C.' COONS E1- AL 2,240,132

EFRIEnA'rIoN Filed .myl 2o, 1958 ,ggmiimiiiiuim l l H i a i a i i a iHema'.

INVENToR Curtis I 60ans VVllzam Ilfzt'to ATTQRN EY Patented Apr. 29,1941 UNITED STATES PATENT OFFICE REFRIGERATION Curtis C. Coons, NorthCanton, and William H. Kitto, Canton, Ohio, assignors to The HooverCompany, North Canton, Ohio, a corporation of Ohio Application July 20,1938, Serial No. 220,187 In Great Britain August 20, 1937 (Cl.(i2-119.5)

16 Claims.

This invention relates to refrigerating systems and more particularly toevaporators designed for use in absorption refrigerating systems.

In refrigerating systems as hertofore constructed, the refrigeratingfluid owed downwardly through the evaporator by gravity. We havediscovered an entirely new principle of evaporation wherein therefrigerant uid is' I caused to circulate upwardly through theevaporator against the force of gravity by the energy supplied from apropelled stream of inert gas vflowing through the evaporator. The broadasrefrigerant from the lowest to the highest portions of the evaporator,it is not always desirable to do so. It may be necessary to constructportions of the evaporator of conduit section of large diameter-so largethat the inert gas velocity is not high enough to drag or sweep theliquid refrigerant through the conduit. It is sometimes necessary ordesirable to supply the liquid refrigerant to an intermediate portion ofthe evaporator to meet structural difficulties. Also it is sometimesnecessary to extend the evaporator a considerable distance above andbelow the 'bottom of the condenser while making avshort directconnection between the evaporator and the condenser. The presentinvention is i designed to meet the above enumerated vdiiliculties in a'simple manner.

We have further discovered that a refrigeratv ing system embodying anevaporator in which the liquid is dragged or swept therethrough by apropelled stream of inert gas is self-regulating for atmospherictemperature changes. That'is, the system automatically regulates itselfto compensate for internal changes induced by variations in atmospherictemperature conditions. This renders unnecessary the complex andexpensive auxiliary equipment previously used to accomplish this result.Our present evaporator is so designed that a Other objects-andadvantages of the invention will become apparent as the descriptionproceeds when taken in connection with the accompany-- ing drawing inwhich: Y

Our invention is diagrammatically illustrated as being applied to athree-uuid absorption refrigerating system having the evaporator there#of shown in perspective and on an enlarged scale.

We have illustrated our invention as applied to a continuous three uidabsorption refrigerating system comprising a boiler B, an analyzer D, arectifier R, a condenser C, an evaporator E, an absorber A, and apressure equalizing medium circulating fan F driven by a motor M. Withthe exception ofthe evaporator E, all elements of this system areillustrated diagrammatically,

it` being understood that they may be of any specic construction or formdesired.

The elements just described are suitably connected by various conduitsto form a complete refrigerating system including a plurality of gas andliquid circuits. 'Ihe system is suitably charged with a refrigerant,such as ammonia,-

evaporator-absorber parts of the ysystem and circulates in a'circuitbetween these elements,

serves to permit the entire system to operate at l substantially thesame pressure while reducing the vapor pressure of the 'refrigerant inthe` evaporator whereforethe refrigerant will evaporate just as thoughthe actual pressure prevailing in the evaporator was materially belowthe condenser pressure. Therefore, no pressure differential need bemaintained between the absorber and generator because the inert pressureequalizing medium present in the absorber p'ermits the samevto operateat an actual total pressure equal to that prevailing in the generatorbut operates with respect to the refrigerant as though the absorber4pressure were much below that prevailing in the generator.

Theboiler B is heated in any suitable manner as by a gas burner or anelectric cartridge heater. The source of heat for the boiler and theelectrical motor M are controlled in any suitable or approved manner. Asuitable control mechanism vis disclosed in the co-pending application'of Curtis C. Coons, led June 1'7, 1937, Serial No. 148,424.

The boiler B contains a solution of refrigerant Y in an absorbent whichwill liberate refrigerant vapor when heated. Refrigerant vapor generatedin the boiler B passes upwardly through the analyzer D in counteriiowrelationship to strong liquor flowing downwardly therethrough.

Absorption solution vapor liberated in the boiler B is condensed in theanalyzer, the heat of condensation serving to generate more refrigerantvapor from the strong solution in the analyzer. The refrigerant vaporpasses from the analyzer to the condenser C through a conduit Il whichincludes the air-cooled rectifier R.- The rectiiier condenses anyabsorption solution vapor which may pass through the analyzer.

The boiler-analyzer system B-D and the absorber A are connected bysuitable conduits to form a solution circuit. Weak solution is conveyedfrom the boiler B through a conduit I2, liquid heat exchanger I3, and aconduit I4 to the upper end of the absorber A through which it flows bygravity. It is apparent that the absorber A is at an elevation higherthan that of the boiler-analyzer system whereby the weak solution mustbe elevated through the conduit I4. For this purpose a small gasbleed-oil conduit I5 is connected between the discharge conduit I5 ofthe fan F and the conduit I4 below the-liquid level of theboiler-analyzer system whereby the liquid is elevated through theconduit I4 by gas lift action. As the solution ilows downwardly throughthe absorber its concentration is increased and the resulting strongsolution is discharged from the bottom of the absorber through a conduitI1 into a strong solution reservoir I3. The strong solution is conveyedfrom the reservoir I3 to the liquid heat exchanger I3 by aconevaporator.

duit I9. Strong solution is returned from the liquid heat exchanger I3to the upper portion of the analyzer D by a conduit 23.

The absorber and the evaporator are interconnected to form a pressureequalizing medium circuit. 'Ihe pressure equalizing medium underpressure discharged from the fan F through the conduit I5 is conveyedinto a gas heat exchanger 22. The gas is conveyed from the gas heatexchanger 22 into the bottom oi the evaporator E through a conduit 23.I'he gas passes'upwardly through the evaporator E in a manner to bedescribedv more fully hereinafter and exits therefrom through a conduit24 into the gas exchanger 22. The gas discharged from .the evaporator isconducted from the gas heat exchanger to the bottom of the absorber by.a conduit 25. After passing through the absorber A, the pressureequalizing medium is returned to the suction inlet of the fan F throughthe conduit 25, thus completing the pressure equalizing medium circuit.

The refrigerant vapor supplied .to the condenser C, which extends wellbelow the top of the evaporator, is liqueiied therein preferably by duit25 to the bottom of the absorber A. 'Ihe mixture passes upwardly throughthe absorber in counterow relationship to the solution ilowingdownwardly therethrough whereby the refrigerant vapor laA absorbed inthe solution and returned to the boiler in the manner previouslydescribed. The purified pressure equalizing medium is then conducted tothe circulating fan F from which it is propelled back to the evaporatorthrough the conduit I6, gas heat exchanger 22 and conduit 23.

Referring now to the evaporator E in detail, it will be seen that itcomprises a plurality of vertically spaced horizontal coil sections 30,3l, and 32 and a box-cooling section 33 which is provided with aplurality of air-cooling ilns 34. The coil sections 30 and 3I areidentical in shape but the conduits forming the coil section 33 are ofan appreciably larger diameter for a purpose to be explainedhereinafter. The coil section 30 only will be described in detail, itbeing understood that the description will apply equally well to thecoil section 3l. The coil section 30 comprises four spaced parallelhorizontal conduit elements. 'Ihe outer conduit elements 35 and 35 areserially connected by a conduit 31 extending across the rear of theevaporator. The inner conduits 33 and 33 are serially connected to theouter conduits 35 and 35, respectively, at the front portion of the Theinner conduits 33 and 35 form the inlet and outlet connection of thecoil section. The top coil section is identical in shape with the coilsection 30 except that it is not provided with a member corresponding tothe conduit section 33, instead, the outer conduit thereof correspondingto the conduit 35 is connected to the 1front end of the box-coolingevaporator section 33 by means of a curved riser conduit 4II. The outletof the coil section 30 is connected to the inlet oi the coil section 3Iby a riser conduit 4I. The riser conduit 4I comprises a pair ofinterfitting sections 5I and 52. The section 5I forms a continuation ofthe conduit 33 of the coil section 30 and extends a substantial part ofthe distance between the coil sections 33 and 3|. The section 52 forms acontinuation of the conduit 39 of the coil section 3| and extendsdownwardly into the section 5I for a purpose to be describedhereinafter. The outlet of the coil section 3| is connected to the inletof the coil section 32 by a riser conduit 42.

The evaporator just described is well adapted to be enclosed in acasingwith the coil sections 30 and 3I forming shelves upon which ice trays orice tray supporting plates may be supported conveniently.

'I'he lean gas conduit 23 is connected to the inlet conduit 33 of thebottom coil section 33 of the evaporator E and the box-cooling section33 oi the evaporator is connected to the rich gas conduit 24 whereby thepressure equalizing medium travels continuously through the evaporatorfrom the bottom to the top thereof.

The liquid refrigerant supplied to the conduit 21 is conducted into theriser conduit section 52 just above lthe point at which it enters theconduit section 5 I.

A drain conduit 45 is connected to the strong solution conduit I3 andthe bottom portion of the inlet conduit 33 adjacent its point ofconnection with the gas supply conduit 23. Foreign matter. such asabsorption solution, and excess liquid refrigerant which nd their wayinto the evaporator are disposed of through the drain conduit 45 or areswept into the absorber with the rich gas from the evaporator.

When the refrigerating system is operating. the pressure equalizingmediur'n is placed under pressure by the fan F whereby it iscaused tocirculate through the system with considerable velocity. The pressureequalizing medium circulating through the relatively large conduitforming the coil section 30 is travelling at a relatively low velocityas compared with that prevailing in the higher portions of theevaporator.

4supplied through the conduit 21 partly flows downwardly through theriser conduit 52 and through the lowest coil section 30 in counterowrelationship with the inert gas streamV passing therethrough. Thebalance of the liquid refrigerant supplied to the riser conduit 4I isdragged or swept by the inert gas stream into the coil section 3|. 'I'hegas stream is moving at a relatively high velocity through the coilsections 3l and 32 and the riser conduits 42 and 40 whereby it is ableto drag or sweep liquid refrigerant through these`coil sections andriser conduits into the box-cooling conduit section 33.

A divided body of liquid refrigerant is supportedin the riser conduitsthrough which the inert gas drags or sweeps its way carrying liquidrefrigerant into the next higher evaporator section. The riser conduit52 is continued downwardly into, the conduit system 3B and 5I a distancejust sufficient to permit the inert gas to support a liquid column inthe section 52 whereby a part of the liquid supplied to the section 52is dragged or swept into the coil section 3l and a part falls into theenlarged coil section 30. The velocity of the inert gas flowing in therator, and with the total system pressure ranging between 270 and 400pounds per square inch.

The above dimensions are cited by way of example only and are notlimiting in any. sense.

The leanest gas is supplied to the bottom portion of the` evaporator butonly sufcient liquid refrigerant flows downwardly from the liquid in-Alet to produce the desired amount of refrigeration`therein. 'Iherefrigerant vapor pressure of the gas stream owing upwardly through theevaporator preg 'essively increases whereby evaporation occurs in thebox-cooling conduit 33 large diameter coil section 30 is not sufficientto drag or sweep the refrigerant liquid along with it whereby the liquidcounterilows with respect to the gas stream. The liquid in the coilsection 30 evaporates into the inert gas stream; any impurities andexcess liquid refrigerant are disposed of through the drain 45.

In order to produce refrigeration efliciently and at the temperaturesnecessary to freeze ice and to pr fserve foodstuffs in domesticrefrigerating ca inets, it has been found advanta geous to circulate theinert gas through the evaporator under conditions such that the vol-.-

umeA of the inert gas will be several hundred times the volume of liquidrefrigerant supplied to the evaporator per `unit of time. Consequently,the velocity of flow of the inert gas through the evaporator will bematerially greater than the velocity of flow of the liquid refrigerant.This evaporator meets that condition ideally while circulating theliquid refrigerant upwardly through all portions of the evaporator.Several factors have a material bearing on the design of an apparatuswhich will produce the desired conditions. The lifting power of theinert gas stream is a function of its density, pressure, and velocity offlow through the evaporator. In general, an increase in the value of anyone or more of the above enumerated factors results in an increase inthe lifting power of the inert gas. Other things being equaL' thevelocity of the inert gas will be a function of the effectivecross-'sectional area of its path of flow; an increase in eectivecross-sectional area of that path resulting in a decrease in gasvelocity. For example, it has been foundthat a propelled stream ofnitrogen will circulate liquid ammonia upwardly through an evaporatorconstructed of approximately one-half inch inside' diameter tubingand'having a vertical height of approximately ten inches, a pressuredifferential of between' two and four inches of water between at atemperature sufficiently high to prevent or minimize frost depositionthereon.

The bodies of liquid present in the various parts of the evaporatorcoils and particularly in the riser conduits have a marked throttlingeffect on the inert gas stream; furthermore this throttling effect ismore noticeable at low pressures than at high pressures. This factormakes the system self-regulating for external atmospheric temperatureconditions for the following reasons: A rise in atmospheric temperaturedecreases the efficiency of the absorber whereby the ammonia vaporpressure of the inert gas stream discharged from the absorber increases;

now able to pick up a lesser quantity of ammonia vapor therebydecreasing the amount of refrig- Y eration available.v But an increasein the tem- Iperature of the atmosphere causes an appreciable vincreasein the pressure of the uids in the system. This increases the density ofthe gas in the pressure equalizing medium circuit. As the density of thepressure equalizing medium increases, the circulating fan causes it tobe placed under a higher pressure and to circulate at a higher velocity.Therefore, an increase in the temperature of the atmosphere decreasesthe efficiency of the absorber but automatically causes a greaterquantity of inert gas to be circulated through the evaporator wherebyrefrigerating capacity is maintained under all atmospheric conditions.

y The liquid progressively and continuously diffuses or evaporates intothe inert gas stream to produce refrigeration whether it is travellingin liquid refrigerant to be swept into the gas heatl 'exchanger or toflow into the drain conduit 45.

The action of the inert gas on the. liquid refrigerant may be brieflydescribed as follows: In substantially horizontal conduits the gasstream iiows over a stream of liquid in the bottom portion of theconduit to which it imparts a propelling force by the frictional drag ofthe gas stream as it passes over the liquid. Additionally, the draggingaction of the gas on the liquid serves to agitata theliquidstream whichimproves the gas and liquid contact therebetween and aids theevaporatin'g process. In the elevating or rising conduits, the -gasstream .supports a body of liquid in a divided state through which thegas continuously forces itself agitating such body of liquid and blowingor dragging a por,

in a relative sense because the velocity of the.

gas will depend upon the conditions prevailing in the particular systemas noted above; for example, in the particular embodiment of theinvcntion disclosed herein, the velocity of gas flow through theevaporator is of the order of a few feet per second if a dense gas, suchas nitrogen, is utilized.

The flow of inert gas through the evaporator Lis .substantiallycontinuous and steady though there is a pressure gradient from the inletto the outlet portions thereof due to the throttling action of theliquid, particularly in rising conduits, on the gas stream. This insuressubstantially continuous uniform propulsion of liquid Athrough theevaporator and continuous production of refrigeration whenever therefrigerating mechanism is operating.

While we have illustrated and described but a single embodiment of ourinvention it is to be understood that it is capable of expression inmany other constructional forms and variations -without departing fromthe spirit of the invention or the scope of the appended claims.

We claim: 1. Refrigerating apparatus comprising a pressure equalizingmedium circuit including an upstanding evaporator and an absorber, asolution circuit including a boiler and said absorber, means forcirculating a pressure equalizing medium through said pressureequalizing medium circuit in such direction that it ows upwardly throughsaid evaporator and said absorber, a gas lift pump for elevatingabsorption solution into the top portion of said absorber, meansdiverting a portion of fsaid pressure equalizing medium into said gaslift pump, means for lique.- fyng refrigerant vapor generated inv saidboiler and for supplying thesame to an intermediate portion of saidevaporator, the arrangement being such that a portion of said liquidrefrigerant flows downwardly through said evaporator in counterflowrelationship to said pressure equalizing'medium and the balance of saidliquid is frictionally elevated through said evaporator by the gasstream owing therethrough.

2. Refrigerating apparatus comprising a pressure equalizing mediumcircuit including an evaporator and an absorber, a solution circuitincluding a boiler and said absorber, means for propelling pressureequalizing medium through said pressure equalizing medium circuit, meansfor circulating solution through said solution circuit, said evaporatorcomprising a plurality of vertically spaced sections serially connectedand connected to said pressure equalizing medium circuit in such fashionthat pressure equalizmg medium Iilows upwardly through said sections,means for liquefying refrigerant vapor generated in said boiler and forsupplying the same to an intermediate portion of said` evaporator, thearrangement being such that a portion of said liquid refrigerant flowsdownwardly through said evaporator in counterilow to said pressureequalizing medium as it evaporates thereinto and the remainder of saidliquid refrigerant is carried upwardly through said evaporator sectionby said pressure equalizing medium as it evaporates thereinto.

3. That improvement in the art of refrigeration which includes the stepsof evaporating liquid refrigerant into an inert gas flowing in counterowrelationship thereto in a first zone and evaporating liquid refrigerantinto said inert gas as it is being conveyed thereby through a secondzone and at temperature levels higher than that prevailing in said rstmentioned evaporating zone.

4. Refrigerating apparatus including an evaporator comprising aplurality of vertically spaced serially connected sections, means forpropelling a pressure equalizing medium upwardlythrough said sections,means for supplying liquid refrigerant to said evaporator intermediate apair of adjacent sections, the arrangementbeing such that a portion ofthe liquid flows downwardly counter to the gas stream into the lower ofsaid pair of sections and the remaining portion of the liquid is carriedby said gas stream upwardly into said upper pairV of sections by thefrictional drag of the gas stream flowing thereover.

5. That improvement in the art of refrigeration which includes the stepsof propelling pressure equalizing medium through` an evaporating zone,flowing one body of liquid refrigerant through said evaporating zone bythe frictional drag exerted thereon by said pressure equalizing medium,flowing another body of liquid refrigerant in said evaporating zonecounter to said pressure equallzing medium, and regulatingthe rate offlow of said pressure equalizing medium in accordance with ambientconditions.

6.- That improvement in the art of refrigeration' which includes thesteps of condensing refrigerant to liquid phase by heat exchange withatmospheric air, supplying said liquid to an evaporating zone,propelling a pressure equalizlng medium through said evaporating zoneand an absorbing zone, circulating an absorbent through said absorbingzone, rejecting the heat of absorption to the surrounding air,circulating liquid refrigerant through said evaporating zone in parallelilow relationship and in counterflow relationship with the pressureequalizing medium, and regulating the rate of flow of the pressureequalizing medium in accordance with the condition of the surroundingair.

7. Absorption refrigerating apparatusv comprising an inert gas circuitincluding an evaporator and an absorber, power driven means forcirculating an inert gas through said circuit, a solution circuitincluding a boiler and said absorber, means for supplying refrigerantgenerated in said boiler to said evaporator in liquid phase, saidevaporator including a low section having a large diameter passagewaytherethrough, an upper section having a small diameter passagewaytherethrough, a riser conduit including interiitting extensions of each`of said evaporator sections, the arrangement being such that liquidrefrigerant is supplied to the extension of said section having a smalldiameter passageway therethrough adjacent its junction with said sectionof large diameter.

8. That improvement i1: the art of refrigeration which includes thesteps of supplying a body of liquid to be evaporated to an intermediateportion of an evaporating zone, owing a portion of `such liquiddownwardly in counterflow relationship to a low velocity stream of aninert pressure equalizing medium, and circulating the balance of saidrefrigerant upwardly through said evaporating zone by .the frictionaldrag exerted thereon by a high velocity stream of inert gas flowingthrough said other portion of said evaporating zone.

9. Refrigerating apparatus comprising means v for producing refrigerantvapor, means for con- 'densing the vapor so produced, an evaporatorincluding a portion of large cross-sectional area` joined to a portionof small cross-sectional area `which extends upwardly above at least aportion of said condensing means, means for supplying liquid from saidcondenser to said evaporator adjacent the junction of said portions oflarge and small cross-sectional area, and means for propelling apressure equalizing medium through said evaporator to circulate aportion of said liquid through said evaporator section of smallcross-sectional area by the impetus imparted to the liquid by the highvelocity gas stream flowing through said portion of smallcross-sectional area.

10. An absorption refrigerating apparatus comprising an inert gascircuit including an evaporator and an absorber, a solution circuitincluding a boiler and said absorber means for liquefying refrigerantvapor generated in said boiler said evaporator including a section ofsmall cross-sectional area and a section of, large cross-sectional area,means for circulating the inert gas through said evaporator withsufficient force lto propel liquid refrigerant through said section ofsmall cross-sectional area, and means for supplying refrigerant liquidfrom said liquefying means to said evaporator adjacent the junctionpoint of said sections of different cross sectional area, whereby aportion of such liquid iiows through said section of large cross-sectionby gravity.

11. An absorption refrigerating apparatus comprising an inert gascircuit including an upstanding evaporator and an absorber, a` solutioncircuit including a boiler and said absorber,

means for liquefying refrigerant vapor generated in said boiler, saidevaporator including an upper section of small cross-sectional area anda lower section of large cross-sectional area, means for supplyingrefrigerant liquid from said liquefying means to said evaporatoradjacent the junction point of said sections of differentcross-sectional area, and means for circulating the inert gas upwardlythrough said evaporator with sufficient force to propel liquidrefrigerant through said section of small cross-sectional area, wherebya portion of the liquid refrigerant ows through said evaporator with theinert gas and another portion thereof ows through said evap oratorcounter to the direction of ow of the inert gas.

12. A combined liquid dividing and elevating device comprising adownwardly extending conduit, an upwardly extending conduit joined tosaid rst mentioned conduit and of smaller cross-sectional area, meansfor propelling a gas through said conduits in a direction to flow firstthrough said downwardly extending conduit and with suflicient force topropel liquid through said upwardly extending conduit but withinsumcient force to propel liquid through said downwardly extendingconduit, and means for supplying liquid to said conduits adjacent theJunction point thereof.

` 13.*An absorption refrigerating apparatus comprising an inert gascircuit including an evaporator and an absorber, a solution circuitincluding a boiler and said absorben'means for liquefying refrigerantvapor generated in said boiler, said evaporator including an uppersubstantially horizontal conduit section of relatively smallcross-sectional area and a lower substantially horizontal conduitsection' of relatively large cross-sectional area, a riser conduitconnecting said sections and including portions of large and of smallcross-sectional area, means for supplying refrigerant liquid from saidliquefying means to said evaporator adjacent the junction point of saidsections of diiferent crosssectional area, and .means for circulatingthe inert gas through said evaporator with suilicient force to propelliquid refrigerant through said section of small cross-sectional area.

14. That improvement in the art of absorption refrigeration whichincludes the steps of expelling refrigerant vapor from solution by theapplication of heat thereto, liquefying the vapor so expelled, conveyinga portion of the liquid into the presence oi a stream of dense gasilowing with a velocity suiiicient to propel the liquid as it isevaporating, flowing another portion of the liquid" into the presence ofa stream of dense gas flowing with a velocity insuiilcient to impart apropelling force to the liquid, and absorbing the refrigerant vapor fromsaid bodies of gas by contacting the same with solution pr'eviouslyweakened by the expulsion of refrigerant vapor therefrom.

15. Absorption refrigerating apparatus of the pressure equalized typeincluding an evaporator element in which a transfer of refrigerant vaporoccurs between a refrigerant liquid and an inert pressure equalizingmedium, an absorber element in which a transfer of refrigerant vaporoccurs between an absorbing liquid and said inert pressure equalizingmedium, means for producing refrigerant liquid and for supplying thesame to said evaporator element, means for conveying absorbing liquid toand from said absorber element, one of said elements having a portion oflarge cross-sectional area joined to a portion of small cross-sectionalarea, and means for propelling the inert pressure equalizingmediumthrough the portion of said one element of small cross-sectional areaunder sufficient pressure and velocity to propel the liquid therethroughas a transfer of refrigerant vapor is occurring between the liquid andthe inert pressure equalizing medium, said one element being so arrangedthat liquldsupplied thereto is supplied adjacent the junction of saidpoijtions of large and A:small cross-sectional area whereby the liquidflows through the portion of said one element of large cross-sectionalarea by gravity as a vapor transfer occurs between the liquid and theinert pressure equalizing medium.

16. Absorption refrigerating apparatus of the pressure equalized typeembodying an element having a passageway in which an inert pressureequalizing medium is in intimate contact with a liquid to effect atransfer of a refrigerant vapor between the liquid and the inertpressure equalizing medium accompanied by a transfer of heat through thewall oi' said passageway, said element including a portion of largecrosssectional area designed for a gravity iiow of liquid and a portionof small cross-sectional .area joined to said portion of largecrosssectional area, means for propelling theinert pressure equalizingmedium through said element with suftlcient pressure and velocity todistribute liquid through said portion of small cross-sectional area andto pass into and out of the distributed liquid, and means for supplyingliquid to said element adjacent the junction of said portions of largeand small cross sectional area whereby a part of the liquid isdistributed through said portion of small cross-sectional area by theinert pressure equalizing medium and another part of the liquid flowsthrough said portion of large cross-sectional area by gravity.

. CURTIS C. COONS.

WILLIAM H. KI'I'I'O.

